Diaphragm cell

ABSTRACT

A novel diaphragm cell (electrolyzer) useful for electrolyzing brines to produce chlorine and sodium hydroxide is disclosed which is constructed of a plurality of single cells. Such single cells are made up from bipolar electrodes which have a plurality of finger-like, dimensionally stable anodes extending in one direction outwardly from a support wall and a plurality of finger-like cathodes extending in the opposite direction from the support wall. In its assembled state, the electrolyzer is made up of one or more single cells in which cathodes of one bipolar electrode are interleaved between anodes of the adjacent bipolar electrode to form a single cell. An especially effective bipolar electrode has hollow anodes having spaced pairs of anode surfaces. In a preferred embodiment the support wall (or backplate) has a titanium surface on its anode side and an iron surface on its catholyte side.

[lll 3,910,827

[451 Oct.7,1975

United States Patent Raetzsch et al.

U.S. Patent Oct. 7,1975

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S8 INVENTORS CARL W. BETZS'CH :i Joy/J F. VnA/Hoozf w #06H cum/momATTORNEYJ DIAPHRAGM CELL RELATED APPLICATION This is a continuation ofapplication Ser. No. 160,339, filed July 7, 1971, which is acontinuation-inpart of application Ser. No. 54,816, filed July I4, 1970,and application Ser. No. 836,082, filed June 24, 1969, all nowabandoned.

THE INVENTION The invention is concerned with an electrolytic cell (orelectrolyzer) in which aqueous alkali metal salts (e.g., sodiumchloride) are electrolyzed to form chlorine and alkali metal hydroxide(so called alkali chlorine cells) of the type which includes asuccession of vertical electrodes in which dimensionally stable anodesalternate with cathodes carrying a diaphragm. It is particularlyconcerned with the arrangement and configuration of the anodes andcathodes on a support wall (or backplate) and with means for securingthe electrodes to the support wall. It is also concerned with a specialbipolar electrode configuration which among other things ischaracterized by hollow anodes having spaced pairs of anodic surfaces.

A variety of types of alkali-chlorine electrolytic cells employing abipolar electrode assembly and a permeable diaphragm have been known inthe past. The present trend in this type of cell is to provide within asingle cell housing a plurality of individual cell units utilizingbipolar electrode structures. See U.S. Pat. Nos. 2,858,263 and3,337,443. ln such an electrode structure, the anodes of one cell arepositioned in a back-toback relationship with the cathodes of theadjacent cell and electrical Contact is maintained between the two. Thesupporting wall for the anodes and cathodes in the back-to-backrelationship functions to physically sepa` rate the cells within theover-all cell housing.

The present invention provides an improved bipolar alkali-halogendiaphragm cell of the described type. The present invention provides adiaphragm cell which is particularly light in weight and easy toassemble and disassemble. lt provides a unique, highly advantageousbipolar electrode configuration which advantageously effects brinecirculation within the cell, reduces (even substantially eliminates) theproblems of gas binding in the interelectrode space and utilizesefficiently metallic anodes. The present invention furthermore providesa diaphragm cell having improved electrical connection between thecathode and anode.

Herein the term cell unit is used to describe the backto-back bipolarassembly of the anodes of one cell with the cathode of the adjacentcell. Each cell thus is made up of cathodes from one cell unit (i.e. thebipolar electrode thereof) interleaved and spaced from anodes of thenext adjacent cell unit (i.e. the bipolar electrode thereof). Each cellunit thus includes as a principal component a bipolar electrodeassembly. The cathodes characteristically have elongated hollow portionswhich are interleaved or interpositioned with and spaced from the anodesof the next adjacent cell unit. The cathodes are constructed of metalwire screening or the like perforated sheeting and are covered with apermeable diaphragm, for example asbestos. The metal wire screening maybe of any suitable metal, for example, steel or, alternatively, nickelor chromium or other metal sufficiently resistant to corrosion under theconditions prevailing in the catholyte during electrolysis.

The finger-like anode elements may be provided by a single sheet orwall-like element or according to a particular preferred embodiment arehollow and cornprise a pair of laterallyspaced vertical walls. Thesewalls, in one embodiment, may be open along the outer end of theelements or alternatively closed or substantially closed at the outerend. Electrolyzers with hollow anodes are constructed so as to providefor the presence of electrolyte in the hollow of the anode. Anodicproducts, notably gaseous chlorine can form and/or collect behind theanode surface directly facing the surface of the adjacent cathode. Thisis gases, notably elemental chlorine can and does collect in the hollowof the anode, and hence its accumulation in the interelectrode space isminimized or avoided. Electrolyte is also free to circulate in theelectrolyzer and to move in the anode hollow. Such circulation of gasand electrolyte is especially noticeable (and enhanced) with metallicanode side walls of previous material, such as when the walls are ofrods, screen, expanded metal mesh, perforated plate or louvered plate.

These anodes are constructed of any suitable chlorineresistant metalsuch as titanium or like valve metal, e.g., tantalum and tungsten,having an electroconductive surface of a platinum group metal or theoxide of a platinum group metal. one or both surfaces of the hollowanodes will have this electroconductive surface. Characteristically, thesheet or wall-like anodes are thin, eg., less than about a half inchthick. The term single-cell is used to describe the cell formed by thefinger-like anodes from one bipolar electrode (or of one cell unit)which are interleaved with the finger-like cathodes from an adjacentbipolar electrode (or of the adjacent cell unit).

Another important component of the cell unit (and bipolar electrode) isthe supporting wall or backplate. As shown in the specific embodimentshereinafter described, the backplate may serve one or more purposesincluding that of l) the prime structural element for supporting theplurality of anodes and cathodes which make up the cell unit, (2) theprincipal structure which divides the entire electrolytic cell(electrolyzer) into its component cells (single cells) and (3) theconductor by which the current flows from cell to cell. For thebackplate to perform such functions it should be of appropriateconstruction and materials. One especially useful type ofelectroconductive backplate has its anodic side (or surface) of titanium(or like valve metal) and its cathodic surface of steel. These surfacesare each resistant enough to the respective cell environments to whichthey are exposed during cell operation to provide for long backplatelife.

In the drawings:

FIG. l shows a perspective view illustrating generally the bipolar cellof the present invention with portions of the cell housing broken away.

FIG. 2 shows in cross-section an enlarged portion of the electrodestaken along the line lI-II in FIG. l illustrating the relationsip of thecell units to the cells in the cell housing.

FIGS. 3-12 illustrate various embodiments for mounting the electrodes tothe support wall in the cell units of the bipolar cell.

FIGS. 13-15 show another preferred embodiment of the present invention.

Bipolar diaphragm cell l0 as shown in FIG. l is constructed of aplurality of cell units such as cell units l l,

l2, 13 and 14 which form single cells 18, 19, and 20. The end cell unitl1 provides a cathode half cell and the end cell unit 14 provides ananodic half cell. The intermediate cell units 12 and 13 are bipolarproviding an anodic surface in the direction of cell unit ll and acathodic surface in the direction of cell unit 14.

The bipolar cell l may be provided with only one intermediate cell unithaving but one bipolar electrode such as cell unit 12. Alternatively,the cell unit l0 may include two or more (frequently 12 or l5)intermediate cell units, as desired. The intermediate cell units may beidentically constructed.

The cell unit 13, for example, has a frame 21 including a backplate 22,which serves as a partition between single cells 19 and 20, andperipheral walls 23, 24, 25 and 26. The frame 21 may be constructed ofiron and steel. However. the anodic side of the backplate 22 and theinner surfaces of walls 23, 24, 25 and 26 Should have a suitableprotective coating, such as of rubber, in order to prevent corrosion.Alternatively, the frame 21 may be of titanium plate or titanium cladsteel plate. The peripheral walls, such as wall 24, each includes a pairof flanges 27 and 28 that allow for bolting the cell unit 13 to similarflanges on the adjacent cell units l2 and 14. Of course, the bolts aresuitably insulated electrically from the cell units and sealing gasketsare provided between the meeting surfaces of the adjacent flanges. Thus,the container for the single cell 19 is provided bythe backplate 22 ofcell unit 13, the peripheral walls 23, 24, 25 and 26 and the backplate22 of cell unit l2.

The backplate 22 in the electrolytic cell illustrated in FIG. l has atleast one opening 34 which allows brine to flow from one cellcompartment to the next thereby providing an equal level of brine ineach single cell. The backplate 22 further includes openings 33 formounting of the cathode 16 and 17 thereon as hereinafter described. Theupper portion of backplate 22 provides means for removing the cathodicgas product, for example, hydrogen, from the cell such means including achamber 37 defined by wall 38 and the upper peripheral wall 25. The wall38 has an opening 39 for passage of hydrogen formed in the hereinafterdescribed cathodic zone in the cell into chamber 37. The hydrogen gas isremoved from chamber 37 through pipe 41. A pipe 42 in the upperperipheral wall 25 is provided for removal of the anodic gas product,for example, chlorine gas which is formed in the anodic zone of thecell. A pipe 43 is provided in upper peripheral wall 25 for passage ofbrine into the single cell. The cell products such as caustic soda areremoved from the cathodic zone of the cell through pipe 44 in the wall24.

The cathode 16, as shown in FIGS. l and 2, includes a backscreen 47spaced from plate 22 and finger-like cathode elements 46 which extendperpendicularly from the backscreen 47. The finger-like cathode elementsare preferably wedge shaped as shown in FIGS, l and 2, thus facilitatingachievement of near zero gap (or interelectrode space) between the anodeand cathode fingers. However, the side walls comprising each cathodecould be substantially parallel with each other. The cathode lingers 46and the back screen 47 may be constructed of material conventionallyused in diaphgram cell cathodes for example, the type of screendisclosed in U.S. Pat, No. 3,337,443. Cathode finger 46 includes theside walls 45 and 50 which are joined at their outermost end and attheir upper and lower edge thus forming a chamber enclosed except forthe end which open into the chamber defined by the backplate 22 and thebackscreen 47. The chambers 70 and 75 of each of the multiplicity ofcathode elements associated with the one cell unit together comprise thecathodic zone (in which the catholyte is contained) of the single cell20. Each cathode element comprising cathode fingers 46 and thebackscreen 47 is electrically interconnected to the backplate 22 and itscorresponding anode 17 of the cell unit. The screen of the cathodefmgers 46 and backscreen 47 is covered with permeable diaphragm suitablyof non-woven asbestos fabric. Alternatively, the permeable diaphragm maybe a permionic membrane. The permeable diaphragm prevents undue mixingof the catholyte and anolyte and allows for the collection of anodic andcathodic gases. The chambers 70 and 75 communicate with the cathodic gascollection chamber 37 through the opening 39 in wall 38.

The cathode fingers 46 each have a plurality of horizontal bars 48including laterally extending flanges 49 for supporting the screenforming the cathode fingers and for conducting electrical current to thecathodes. The bars 48 may be constructed of the same type of material asused in backplate 22, for example, iron or steel.

The anodes 17 (FIGS. l and 2) are finger-shaped and extend outwardlyfrom the backplate 22. Anode 17 includes a pair of laterally-spacedwalls 61 and 62 and a rear wall 63. The walls 61 and 62 may be solidplate or may be of a foraminous or louvered sheet material. Anode 17 hasa horizontal bar 64 with laterallyextending flanges 66 for support ofthewalls 6l and 62. The walls 61 and 62 preferably are disposed so thattheir outer surfaces are at an angle which is complementary to the angleprovided between the pair of adjacent cathode fingers 46. Thus, when theelectrodes are in position of operation shown in FIG. 2, a uniform space(electrode gap) is provided between the outer, opposed, facing surfacesof the respective anodes and cathodes. The anode 17 including walls 6l,62 and 63 as well as the horizontal bar 64 and flanges 66 and 67 may beconstructed of any suitable anodically-resistant material, preferablytitanium. The outer surfaces of solid walls 6l and 62 should be coatedwith a suitably anodically-resistant electroconductive surface Such as aplatinum group metal or the oxide of a platinum group metal such asplatinum, rhodium, palladium, ruthenium, rhenium, and osmium, mixturesand alloys of these metals, and/or one or more oxides of these metals.ln addition, the electroconductive surface may also contain oxides ofother metals, some of which will improve the anodes performanceincluding oxides of titanium, lead, manganese, cobalt, iron, chromium,tanta` lum and silicon. lf the walls 6l and 62 are foraminous sheets,then the outer and/or inner surfaces may be coated with such metal ormetal oxide.

The cathode 16 and anode 17 are mounted on backplate 22 by electrodesupport means 52 (FIG. 2). The electrode support means 52 includes ablock 53 which extends through opening 33 in backplate 22 and is Securedtherein such as by welding. The block 53 may be constructed of iron rodor other electrically conductive, cathodically-resistant material andhas an opening 54 there through for reception of screw S6. The screw 56is threadedly engaged in opening 57 in the corresponding horizontal bar48 of cathode finger 46. The

screw 56 holds the backscreen 47 and the cathode finger 46 snuglyagainst a shoulder S8 of block 53 to provide good electrical contact.The opening 54 in block 53 has an enlarged portion 59 of sufficient sizeto permit the head of the screw S6 to be disposed there within. The rearwall 63 of anode 17 has an opening 68 through which anode mounting screw69 extends for threaded engagement in the enlarged portion 59 of opening54 in the block 53. The open outer end of anode 17 provides access toscrew 69 for mounting and dismounting of anode 17. The screw 69 holdsthe anode 17 securely against block 53 and backplate 22 thus providinggood electrical contact. The screw 69 should be of ananodically-resistant electrically conductive material such as titanium.Sealing gasket 71 may be provided between the anode 17 and the backplate22, thereby preventing any anolyte from reaching the block 53 which, ifit were to happen, might result in corrosion. Seal 73 is providedbetween screw 69 and the backwall 63, thereby preventing leakage ofanolyte through opening 68 and into contact with the block 53.

The end cell unit 14 is constructed identical to cell unit 13 exceptthat cell unit 14 does not include a cathode. In other words, the onlyelectrodes mounted on cell unit 14 are anodes. The anodes may extendthrough the backplate and be welded or bolted to a copper bus bar.

Cell unit l1 is constructed of a backplate 77 which may be bolted tocell unit 12. Cell unit l1 has a cathode 78 including a backscreen 79and finger-like cathodes 80. Cathode 78 may be mounted on plate 77 in amanner identical to the mounting of cathode 16 on backplate 22 of cellunit 13.

The cell units ll, 12, 13 and 14 are bolted together, forming singlecells 18, 19 and 20, and the bolts are suitably insulated to preventshorting between cell units. Alternatively, the cell units may besecured together by tie rods in a manner conventionally used in filterpress type cells. The single cells 18, 19 and 20 are electricallyconnected in series. During a typical operation, brine is continuouslyadded to each of the single cells through the corresponding pipe 43. Theopenings 34 between single cells permit equilization of the brine levelin each single cell. The openings 34 further prevent any one of thesingle cells from going dry, for example, due to a stoppage in pipe 43.The brine is electrolyzed in the single cell with anodic products, suchas chlorine gas being formed in the anodic zone and cathodic products,such as hydrogen gas and caustic soda being formed in the cathodic zone.ln those instances where each anode includes a pair of laterally spacedwalls (e.g., as shown in some detail in FIGS. 3 and l2) of perviousmaterial anodic gaseous products can and will collect in the hollow ofthe anode (bounded by the walls) and rise to the top of the cell forremoval via pipe outlet 42. The diaphragm prevents back migration of thecathodic products into the anodic zone.

As illustrated in FIG. l, anodes 17 have their walls open andterminating above the bottom lower wall of the cell unit. This permitsliquid communication between the interelectrode space and the hollowspace within the anode. Electrolyte can thus also circulate behind theanode walls, and the anolyte in such cell configurations can be regardedas including electrolyte present both between the cathode and anode aswell as within the hollow of the anode.

With perforate (pervious) anode walls, chlorine readily collects andrises in the hollow space defined by the space walls of the anode. Asthis chlorine collects and rises within the hollow, it will causemovement of electrolyte. With anode walls spaced close enough (usuallyspaced laterally less than 5 inches, more often between and 3 inches)and especially when the electrolyzer is operated with reasonably highcurrent densities, the rising chlorine gas will lift upwardlyelectrolyte in the hollow. Electrolyte (anolyte liquor) circulation canprimarily be provided in this fashion by the lift due to rising chlorinegas.

With those electrolyzers having bipolar electrodes with hollowelectrodes as herein contemplated, brine feed to the electrolyzer neednot be directly into the interelectrode gap. Brine, for example, can beintroduced wherever convenient (other than to the catholyte); it can befed into the hollow space of the anodes, if desirable.

It is found that with previous hollow anodes. electrolyzers of the typeherein described function especially well and evidence ruggedness ofperformance. For example, shorting usually attributed heretofore inother cells to touching (or undue closeness) of anodic surface anddiaphragm is no longer a frequent event even though there may be someslight misalignment or touching of anode to diaphragm (or cathodesurface which has lost diaphragms.)

Further preferred embodiments of electrode support means are shown inFIGS. 3-12. The bipolar cell units 12A-121 shown in these Figures areconstructed substantially like cell unit l2 except for the electrodedcsign and electrode support means.

The electrode support means 52A (FIGS. 3 and 4) includes an elongatedbar or current gatherer 81 which is typical of the current gatherer usedin cell units 12A through 12H. The current gatherer is welded to thecathode finger 46A and has openings (not shown) through which cathodicproducts formed in fingers 46A may pass to the chamber 75A. A metalblock 82 is secured to bar 8l such as by welding. The metal block 82extends through an opening 83 in backscreen 47A and is secured tobackplate 22A by screw 84. The screw 84 extends through opening 87 inbackplate 22A and is threadedly engaged in opening 88 in block 82.Preferably, the head 89 of screw 84 is countersunk into backplate 22Athereby providing a flat surface against which anode 16A (FIG. 4) may bemounted The electrode support means 52A further includes a screw 91which secures the anode 16A (FIG. 4) or anode 17A (FIG. 3) to backplate22A. The head 92 of screw 91 is preferably welded to backplate 22A. Inthe embodiment illustrated in FIG. 3 screw 91 is situated along the sameaxis as that of screw 84 whereas FIG. 4 shows an embodiment where screw91 is offset from screw 84. In both embodiments, screw 91 extendsthrough an opening 93 in backplate 22A and an opening 94 in the rearwall 63A of anode 17A (or 16A). The nut 96 is tightened down on screw 91and draws anode 17A or 16A snugly and securely against backplate 22A. Aseal 97 may be provided between anode 17A and backplate 22A, therebypreventing any leakage between the cathodic compartment and the anodiccompartment. A seal 90, such as a Thred Seal (Trademark of Parker SealCompany), is provided between nut 96 and wall 63A.

The bipolar cell unit 12B (FIG. 5) includes an anode 17B, a backplate22B, and a cathode 16B. The electrode support means 52B includes anenlongated bar 101 which is secured to cathode finger 46B, for example,by welding. Openings, not shown, are provided in bar 101 through whichcathodic products may pass. A rod 102 which is threaded at one end issecured to bar 101, such as by welding. The rod 102 extends throughopening 103 in backplate 22B. A nut 104 is threadedly engaged with rod102, thereby securing cathode 16B in place. Preferably, a seal 106 suchas a Thred Seal (Trademark of Parker Seal Company) is provided betweennut 104 and backplate 22B. The seal 106 prevents leakage of catholytethrough backplate 22B to its anodic side. The rear wall 63B of anode 16Bin this em bodiment is a double wall including wall portions 107 and108. The wall portion 107 may be of steel but the wall portion 108 mustbe of an anodically-resistant material such as titanium. The wallportion 107 has an opening 109 through which rod 102 extends. A nut 111secures a wall portion 107 to the backplate 22B. The side walls 61 B and62B extend over wall portion 107 and are welded thereto. A screw 112extends through opening 113 in wall portion 108. The screw 112 may bethreadedly engaged in a suitable opening in rod 102. Alternatively, thescrew 112 may be off set from rod 102, threadedly engaged in a suitableopening in wall portion 107, or screw 112 may be threadedly engaged in anut disposed on the side of wall portion 107 toward backplate 22B. Thescrew 112 thereby secures wall portion or cover 108 to wall portion 107.A seal 114 is disposed between wall portion 108 and wall portion 107 andprevents arolyte from contacting wall portion 107. A further seal 116 isdisposed between anode 16B and the backplate 22B.

The bipolar cell unit 12C (FIG. 6) includes an anode 17C` cathode 16Cand backplate 22C. The anodes 17C and cathodes 16C are secured to thebackplate 22C by the electrode support means 52C The electrode supportmeans 52C includes an elongated bar 121 which is welded to the fingercathode 46C. Bar 121 has openings therein for passage of cathodicproducts. A rod 122 is secured to bar 121 and extends through an opening123 in backplate 22C. The electrode support means 52C further includes anut 124 which is threadedly engaged with rod 122. The nut 124 serves tohold the cathode 16C in spaced relationship to the backplate 22C. A nut125 is threadedly engaged with rod 122 thereby securing cathode 16C tothe backplate 22C. A seal 126 may be located between nut and backplate22C. The anode 17C includes side walls 61C, 62C, and rear wall 63C. Therear wall 63C includes an opening 128 through which extends a screw 129.Screw 129 is threadedly engaged in rod 122 and secures the anode 17C tothe backplate 22C. The screw 129 draws rear surface 127 of wall 63C intoelectrical contact with rod 122 and nut 125. Seals 131 and 132 areprovided to prevent leakage of anolyte into contact with parts which areof materials not resistant to the anolyte, notably steel parts such asrod 122 and backplate 22C,

The cell unit 12D (FIG. 7) includes an anode 17D. cathode 16D, andbackplate 22D. The electrode support means 52D in this embodimentcomprises an elongated bar 141 which is welded to the cathode finger46D, the electrode support means 52D further includes the connectingblock 142 which is attached to bar 141 such as by welding. Th block 142extends through an opening 143 in backplate 22D. The anode 17D issecured in place by screw 144 which extends through opening 146 in rearwall 63D and is threadedly engaged in opening 147 in block 142. Theblock 142, if desiredl may be welded to the backplate 22D.

The electrode support means 52E of bipolar cell unit 12E (FIG. 8)includes an elongated bar or current gatherer 151 which is welded to thecathode t'mger 46E. The electrode support means 52E further includes arod 152 which is welded to the bar 151 and extends through an opening153 in backplate 22E. A nut 154 is threadedly engaged with rod 152thereby holding cathode 16E in place. A seal 156 may be provided betweennut 154 and the backplate 22E. The rod 152 extends through an opening157 in the rear wall 63E of anode 17E. A threaded cap 158 is threadedlyengaged with rod 152 thereby holding anode 17E in place. A seal 159 isprovided between cap 158 and the rear wall 63E. A seal 160 is providedbetween the anode 17 E and the backplate 22E.

The electrode support means 521: of bipolar cell unit 12F (FIG. 9)includes an elongated bar 171 which is welded to cathode nger 46F, ablock 172 which is welded to bar 171 is threaded to that the nut 173 maybe tightened against the rear screen 47F. The block 172 has a portion174 of reduced diameter which extends through the opening 176 in thebackplate 22F. The block 172 has a shoulder 177 which abuts against thebackplate 22F thereby holding the backscreen 47F at a point spaced frombackplate 22F. The screw 178 secures anode 17F to the backplate 22F. Thescrew 178 extends through opening 179 in rear wall 63F and is threadedlyengaged in opening 181 in the block 172. The screw 178 holds the meetingsurfaces of wall 63F and block 172 in electrical contact with oneanother. A seal 182 is provided between the head of screw 178 and wall63F and a seal 183 is provided between anode 1'7F and backplate 22F. Theseals 182 and 183 may be of EPDM rubber (ASTM designation) which hasexcellent resistance to corrosion and remains resilient even afterextended periods of cell operation at high temper atures.

The bipolar cell unit 12G (FIG. 10) has an electrode support means 52Gincluding a current gatherer 191 which is welded to the cathode finger46G. A threaded rod 192 is welded to the current gatherer 191. A nut 193is threadedly engaged with rod 192 and securely holds the backscreen 47Gagainst electrode finger 466. A nut 194 is threadedly engaged with rod192 and holds the cathode 16G in a position spaced laterally from thebackplate 22G. The rod 192 extends through opening 196 in the backplate22G. The anode 17G in this embodiment is a single sheet or plate-likeelement, i.e., in contrast to the embodiments illustrated in FIGS. 2 to9, includes only one side wall comprised of a plate of titanium or atitanium group metal having an electroconductive surface on both sidesthereof. This side wall 61G, when the cell is operating, is disposedsubstantially equi-distant between opposed cathode lingers of eachcathode of the appropriate cathode pair (not shown) of the adjacent cellunit. The anode 17G further includes a rear wall 63G which is welded toanode side wall 61G. The rear wall 63G has an opening 197 through whicha screw 198 extends for threaded en gagement in an opening 199 in therod 192. The screw 198 securely holds the anode 17G in place against thebackplate 22G.

1n the embodiment illustrated in FIG. 10, the anode component of thecell unit is in the form of a thin anodicallyresistant verticallydisposed sheet or plate having substantially parallel flat surfaces ofappropriate electroconductive material upon which anolyte products ofelectrolysis (e.g., chlorine) form. When assembled in the electrolyticcell, each thin anode plate (of which there are a plurality in each cellunit) is interleaved between, but spaced laterally of opposed cathodefingers of adjacent cathodes extending outwardly from the adjacent cellunit.

The vertical edge of the sheet-like anode terminates parallel to andspaced from the backplate of the adjacent cell unit. The lateraldistance (spacing) from this anode edge to the backplage cathodic facewill be substantially greater (at least three times greater, but rarelymore than times) than the space between the anode face and opposedcathode fingers (electrode gap), thus favoring current flow betweenopposed cathode and anode faces. A typical lateral space will be from 2to 8 inches.

These anodes desirably are quite thin, usually considerably less thanone inch in thickness (distance between the anodes parallel faces),notably about 0.5 inches or less (rarely less than 0.2 inch). When thesheet-like anodes are of mesh, thickness as herein intended considersthe mesh as if it were a solid plate.

The cell unit 12H (FIG. l1) includes an electrode support means 52Hhaving a current gatherer 211 which is welded to the finger cathode 46H.The current gatherer 211 may be a discontinuous bar, thus permittingcathodic products to pass from the finger to the space between thescrews 47H and plate 22H. A threaded rod 212 is welded to the currentgatherer 211. A nut 213 is threadedly engaged with rod 212 for purposesof holding the backscreen 47H securely against the fingered electrode46H. The electrode support 52H further includes a nut 214 forcontrolling the extent to which the threaded rod 212 extends through theopening 216 in the backplate 22H` Ribs 223 are provided for spacingscren 47H from plate 22H. The ribs 223 may be of steel or other materialchemically resistant to the catholyte conditions and are welded to plate22H. The screen 47H is slightly flexible, thus permitting adjustment ofrod 212 with respect to backplate 22H. The anode assembly 17H in thisembodiment carries a narrow anode member 217, including a pair of sidewalls 61H and 662H which are welded to the rear wall 63H. A screw 219extends through opening 221 in rear wall 63H and is threadedly engagedin the opening 222 in rod 212. The screw 219 securely retains the anode17B against the backplate 22H and maintains excellent electrical Contactbetween the meeting surfaces of wall 63H and rod 212.

The cell unit 121 (FIG. 12) includes cathodes 161 and anodes 171 whichare mounted on a backplate 221 such as by electrode support means 521.The cathodes 161 may be constructed substantially like cathodes 16 shownin FIGS. l and 2. However, in this instance the rear portions 225 and226 of side walls 451 and 501 are ared thereby providing lingers 461with a wider base for resting against back screen 471 and permittingflexing of cathode 161 during adjustment of the block 228 with respectto backplate 221.

The electrode support means 521 includes a current gatherer 227 which isan elongated bar having openings therein through which cathode productsmay pass. The

current gatherer 227 is welded to side walls 451 and 501 of cathode 161.The electrode support means 521 includes a threaded rod 228 which iswelded to the current gatherer 227 and extends through opening 229 inbackscreen 471 and opening 230 in backplate 221. A nut 233 is threadedlyengaged with rod 228 and retains cathode finger 461 securely againstbackscreen 471. Nut 234 is threadedly engaged with rod 228 and holds thecathode 161, including backscreen 471 and finger 461, securely againstbackplate 221. A screw 236, preferably of titanium metal, extendsthrough opening 237 in rear wall 631 of anode 171 and is threadedlyengaged in opening 235 in rod 228. A titanium thread seal washer 238 isprovided between anode 171 and backplate 221. A plurality of spacer bars241 are provided between backscreen 471 and backplate 221. The bars 241hold the cathode 171 spaced from the backplate 221 and may beconstructed of any material which is corrosion resistant in a cathodeenvironment, for example, steel or copper. The ring nut 234 adjusts thedistance rod 228 extends through plate 221, thus assuring proper contactbetween the surfaces of wall 631 and rod 228. Furthermore, use of ringnut 234 permits use of a smaller screw 236 than would otherwise benecessary. The rear wall 631 may be a continuous wall the full length ofthe anode 171 or may be comprised of a plurality of discontinuous wallportions, for example, one such wall portion being provided for eachelectrode support means. Alternatively, all of the anodes 171 for a cellunit could be mounted on a single rear wall 63|.

Furthermore, wall 221 could serve as the rear wall of anodes 171 inwhich case wall (backplate) 221 may ideally be a titanium clad steelplate and anode walls 611 and 621 may be welded thereto. Wall 221 thusis provided on its anodic face with a titanium surface (anelectroconductive material chemically resistant to the anolyteenvironment) and on its cathodic side with an iron surface (anelectroconductive material resistant to the catholyte environment).Although, because of availability, cost and structural strength,backplates of titanium clad steel are specially preferred, backplatesmay have surfaces of other materials meeting certain electrical andcorrosion resistant standards.

1n lieu of a steel cathodic surface, the backplate may be of otheradequately electroconductive catholyte resistant materials such asferrous metals (iron, alloys of iron including various steels), nickel,copper, gold, cobalt, platinum, silver lead and chromium, or mixturesthereof. Useful metals for the cathodic faces thus are those which donot readily form hydrides (by reaction with atomic hydrogen in thecatholyte) and which are electroconductive. Metals whose resistivity isless than 50 microhms per cubic centimeter (at 20C.) are thus useful,while those with resistivities greater than l but less than about 20microhms per cubic centimeter are especially useful.

On its side exposed to the anolyte, the backplates anodic surface may beof other so called valve metals or precious metals such as tantalum,niobium, platinum, zirconium, ruthenium, palladium, rhodium andirridium. The surface of titanium actually exposed to anolyte has thinprotective titanium oxide film which usually develops in situ if notpreformed. These metals and oxides are resistant to the anolyteconditions to which they are exposed, and particularly are resistant tochlorination, for example. Other oxides which have satisfactorycorrosion resistant properties include magnetite and lead oxide.

As indicated, the respective anodic and cathodic sides of the backplateare of different materials, the most exemplary combination of which istitanium (on the anode side) and steel (on the cathode side) in the formof a single sheet, e.g., titanium clad steel. lt is however possible touse a structure in which a suitable electroconductive metal issandwiched between the titanium and steel, such as a copper sheet havingtitanium on its anode side and steel on its cathode side.

The anodes 17| each include side walls 61| and 62| which are laterallyspaced from one another and which may be secured such as by welding to arear wall 63|. The side walls 61| and 62| of anode 17| are divergingrather than converging. ln other words, the space (and lateral distance)between walls 61| and 62| is less adjacent rear wall 63| than it is atthe edge opposite rear wall 63|. The side walls 61| and 62| may havestiffening rods 242, if desired. The stiffcning rods 242 may be weldedto the outer sides of walls 61| and 62|. ln this embodiment, the cathodelinger 46| lies between the side walls 61| of one anode wall pair and62| of the wall of the next adjacent anode. For further strengtheningproviding improved electrode spacing, the side wall 61| of one anodefinger 17| may be secured at the forward edge thereof to the side wall62| of that next adjacent anode finger, such as by connector 243. Theconnector 243 in this instance includes a screw 244 which extendsthrough an opening in wall 61| and is threadedly engaged in nut 245. ltis possible to bring the forward edges of the anode walls substantiallyinto touching contact by tightening this connecting means. The nut 245is secured to side wall 62| such as by welding. The connector 243alternatively may be a metal clip.

Although the walls of each anode diverge as they extend outwardly fromrear wall 63| in this configuration, laterally spaced walls 62| and 61|each from one of two adjacent anodes which are interposed betweenadjacent cathode fingers converge as they extend towards cathodicbackscreen 47|.

Cell J, shown in FlG. 13-15 is a further embodiment of the presentinvention. Cell 10J is constructed similar to cell 10 of FIG. l. Cell10J has a cell container or frame 21J which. if desired, may beidentical to frame 2| shown in FIG. l. Cell 10J further includes aplurality of wedge-shaped cathodes 16J and anodes 17j which are mountedon backplate 22.1 by an electrode support means 52j. ln this embodiment,the thin edge 255 of wedge-shaped electrodes lies in a horizontal planeor` in other words, the thin edge of the electrodes extendsperpendicular to the vertical backplate 22]. The cathode 16J has a pairof side walls 45] and 50.1, a bottom wall 252, and an outer end wall253. The walls 45.1, 50|, 252 and 253 may be constructed of screen. Thewalls 45| and 50], as shown in FIG. 14, converge upwardly. lf desired,baffles 254 (FlG. 13) may be provided in cathode 16J to force productgases from the cathode wedges into the space between the backstream 47jand the backplate 22]. The anode 17] includes a pair of side walls 61.|and 62j which are preferably constructed of foraminous plates. The anode171 further includes a backplate 63|. The electrode support means 52],shown in detail in FIG. 15, is comprised of a current gathering bar 256which is secured to walls 45.1 and 50] adjacent the open end of cathode16J, for example, by welding. The electrode support means 52] furtherincludes a rod 257 which is secured to bar 256 and extends throughopenings in the backplate 22j and rear wall 63] of anode 17J. A nut 258is threadedly engaged with rod 257, thereby securing anode 17J andcathode 16J to the backplate 22].

The anodes 17 thorugh 171 have generally been described as beingconstructed of a titanium group metal with the walls 6l-61J and 62-62Jbeing solid plates and the titanium plates being platinized on the sideadjacent the cathode fingers 47-47.|. The anodes 17-17J mayalternatively have side walls constructed of a pervious,anodically-resistant plate, for example, of rod material, screen,expanded metal mesh, perforated plate or louvered plate. The perviousplate may be of titanium metal. ln one preferred embodiment, thepervious titanium plate has an electroconductive surface, for example,of platinum, only on the side remote from the cathode fingers. By sodoing, the titanium metal forms a non-conductive titanium oxide coatingadjacent the diaphragm and gas evolution during cell operation takesplace on the back side of the side walls, thus substantially reducinggas blinding and turbulence in the diaphragm. Both sides (surfaces) ofthe perforate anode may be provided with an electroconductive surface.When this is done, it is usually the better practice for theelectroconductive surface facing the diaphragm to be thicker (1.5 to 5times) than the coating 0n the other anode surface facing away from thecathode and toward the hollow of the anode.

Chlorine which evolves on the front side (and thicker electroconductivesurface) of the anode wall nevertheless can move through the openings inthe perforate anode walls into the hollow anode space. Louvered,perforate or expanded metal mesh or like materials with openingsfacilitate such gas movement and also permit anolyte to move from theelectrode gap through the openings into the anode hollow. With thelouvers (or like openings) tilted or fluted upwardly and inwardly towardthe hollow space, gas and liquid movement through the anode walls hasimparted thereto an upward movement component.

Furthermore` the side of the cathode backscreen and cathode fingerstoward the anode may be electrically insulated such as with a rubbercoating. By so doing, the cathodic gas products would be produced on theback side of the cathode which would further reduce gas blinding andback migration of caustic soda. This arrangment would provide ahighly-efficient cell, particularly if the porosity of the diaphragm isslightly increased and the cell is operated at a high brine flow rateand a high current density such as in excess of 150, preferably inexcess of 200, amperes per square foot of cathode surface, as defined bylength and breadth measurements of the cathode. The cell of the presentinvention, especially when using wedge-shaped foraminous anodes andcathodes, operates in a very efficient manner when the anode-to-cathodegap (electrode gap) is near zero, for example, generally less than V2inch, typically, fia to A inch and, preferably, the anode is directlyagainst the diaphragm.

Although the present invention has been described with reference tospecific details of particular embodiments thereof, it is not intendedthereby to limit the scope of the invention except insofar as thespecific details are recited in the appended claims. For example, oneskilled in the art may replace the nonwoven asbestos fabric with apermionic membrane.

We claim:

l. A method of operating a bipolar electrolyzer having a plurality ofindividual bipolar units in back-toback bipolar configuration, with aperipheral wall around each individual bipolar unit; an anolyte chamberand a catholyte chamber in each individual bipolar unit, the anolytechamber and catholyte chamber of an individual bipolar unit beingseparated from each other by a backplate having a surface of a ferrousmetal on the catholyte side and titanium on the anolyte side; aplurality of hollow, wedge-shaped, inward and upward louvered, valvemetal anodes in said anolyte chamber, said valve metal anodes having anelectrically conductive surface thereon; valve metal conductors betweenthe base of said valve metal anode wedges and the titanium surface ofsaid backplate; the bases of said hollow, wedge-shaped, inward andupward louvered, valve metal anodes being held securely against saidvalve metal conductors; a plurality of hollow, wedge-shaped, metalcathodes in said catholyte chamber; said hollow, wedge-shaped metalcathodes being spaced from and electrically connected to the ferrousmetal surface of said backplate; the hollow, wedge-shaped, valve metalanodes of one bipolar unit and the hollow, wedgeshaped cathodes of thenext adjacent bipolar unit being interleaved between and uniformlyspaced from each other and forming a single electrolytic celltherebetween; and a diaphragm therebetween dividing said singleelectrolytic cell into an anolyte chamber and a catholyte chamber; whichmethod comprises feeding sodium chloride brine into each of theindividual electrolytic cells; passing an electrical current through theelectrolyzer from the cathodes of one cell through the backplate to theanodes of the next adjacent cell in the electrolyzer; evolving chlorinein the anolyte chamber; collecting the evolved chlorine within thehollow, wedge-shaped anodes between the inward and upward louvered metalwalls thereof, thereby imparting an upward circulatory motion to anolyteliquor within the hollow, wedge-shaped anodes; recovering said chlorineat the top of said anolyte chamber; evolving hydrogen and caustic sodain said catholyte chamber; recovering said hydrogen at the top of saidcatholyte chamber; and recovering catholyte liquor from said catholytechamber.

2. The method of operating a bipolar electrolyzer of claim 1 whereinsaid hollow, wedge-shaped, inward and upward louvered, valve metalanodes have an electrically conductive surface only on the interiorsurfaces thereof and wherein chlorine is evolved only within the hollow,wedge-shaped anodes.

3. The method of operating a bipolar electrolyzer of claim l comprisingpassing the electrical current from a cathode of one cell through anelectrode support means which extends through an opening in thebackplate, to an anode mounting means of the next adjacent cell of theelectrolyzer, and from the anode mounting means to an anode mountedthereon.

4. The method of operating a bipolar electrolyzer of claim l comprisingcollecting the evolved hydrogen gas in a chamber in the upper portion ofthe bipolar unit and recovering catholyte liquor from a separate chamberin the lower portion of the bipolar unit.

5. A method of operating a bipolar electrolyzer having a plurality ofindividual bipolar units in back-toback bipolar configuration, with aperipheral wall around each individual bipolar unit; an anolyte chamberand a catholyte chamber in each individual bipolar unit, the anolytechamber and catholyte chamber of an individual bipolar unit beingseparated from each other by a backplate having a surface of a ferrousmetal on the catholyte side and titanium on the anolyte side; aplurality of hollow, wedge-shaped, inward and upward louvered, titaniumanodes, in said anolyte chamber, said titanium anodes having anelectrically conductive surface only on the interior surfaces thereof;titanium conductors between the base of said hollow, wedgeshaped,titanium anodes and the titanium surface of said backplate; the bases ofsaid hollow, wedge-shaped, inward and upward louvered, titanium anodesbeing held securely against said titanium conductors; a plurality ofhollow, wedge-shaped, metal cathodes in said catholyte chamber; saidhollow, wedge-shaped metal cathodes being spaced from and electricallyconnected to the ferrous metal surface of said backplate; the hollow,wedge-shaped, titanium anodes of one bipolar unit and the hollow,wedge-shaped cathodes of the next adjacent bipolar unit beinginterleaved between and uniformly spaced from each other and forming asingle electrolytic cell therebetween; and a diaphragm therebetweendividing said single electrolytic cell into an anolyte chamber and acatholyte chamber; which method comprises feeding sodium chloride brineinto each of said individual electrolytic cells; passing an electricalcurrent through said electrolyzer from the cathodes of one cell throughthe backplate to the anodes of the next adjacent cell in theelectrolyzer; evolving and collecting chlorine within the hollow,wedge-shaped anodes between the inward and upward louvered wallsthereof, thereby imparting an upward circulatory motion to anolyteliquor within the anode wedges; recovering said chlorine at the top ofthe anolyte chamber; evolving hydrogen and caustic soda in the catholytcchamber; recovering said hydrogen at the top of the catholyte chamber;and recovering catholyte liquor from the catholyte chamber.

6. The method of operating a bipolar electrolyzer of claim 5 comprisingpassing the electrical current from a cathode of one cell through anelectrode support means which extends through an opening in thebackplate, to an anode mounting means in the next adjacent cell, andfrom the anode mounting means to an anode mounted thereon.

7. The method of operating a bipolar electrolyzer of claim 5 comprisingcollecting the evolved hydrogen gas in a chamber in the upper portion ofthe bipolar unit and recovering catholyte liquor from a separate chamberin the lower portion of the bipolar unit.

8. A method of operating a bipolar electrolyzer having a plurality ofindividual bipolar units in back-toback bipolar configuration, with aperipheral wall around each individual bipolar unit; an anolyte chamberand a catholyte chamber in each individual bipolar unit, the anolytechamber and catholyte chamber of an individual bipolar unit beingseparated from each other by a backplate having a surface of a ferrousmetal on the catholyte side and titanium on the anolyte side; aplurality of hollow, wedge-shaped, inward and upward louvered, valvemetal anodes in said anolyte chamber, said valve metal anodes having anelectrically conductive surface only on the interior surfaces thereof;valve metal conductors between the base of said hollow. wedge-shaped,valve metal anodes, and the valve metal surface of said backplate; thebases of said hollow,

wedge-shaped, inward and upward louvered, valve metal anodes being heldsecurely against said valve metal conductors; a plurality of hollow,wedge-shaped, metal cathodes in said catholyte chamber; said hollow,wedge-shaped, metal cathodes being spaced from and electricallyconnected to the ferrous metal surface of said backplate, the hollow,wedge-shapedl valve metal anodes of one bipolar unit and the hollow,wedgeshaped cathodes of the next adjacent bipolar unit being interleavedbetween and unformly spaced from each other and forming a singleelectrolytic cell therebetween; and a diaphragm therebetween dividingsaid single electrolytic cell into an anolyte chamber and a catholytechamber; which method comprises feeding sodium chloride brine into eachof said individual electrolytic cells; passing an electrical currentthrough said electrolyzer from the cathode of one cell through anelectrode support means which extends through an opening in thebackplate, to an anode mounting means, in the next adjacent cell, andfrom the anode mounting means to an anode mounted thereon; evolving andcollecting chlorine within the hollow, wedge-shaped, valve metal anodesbetween the inward and upward louvered walls thereof, thereby impartingan upward circulatory motion to the anolyte liquor within the hollow,wedgeshaped anodes; recovering said chlorine at the top of said anolytechamber; evolving hydrogen and caustic soda in said catholyte chamber;collecting the evolved hydrogen gas in a chamber in the upper portion ofthe bipolar unit and recovering the hydrogen gas therefrom; andrecovering catholyte liquor from a separate chamber in the lower portionof the bipolar unit.

9. A method of operating a bipolar electrolyzer having a plurality ofindividual bipolar units in back-toback bipolar configuration, with aperipheral wall around each individual bipolar unit; an anolyte charnberand a catholyte chamber in each individual bipolar unit, the anolytechamber and catholyte chamber of an individual bipolar unit beingseparated from each other by a backplate having a surface of a ferrousmetal on the catholyte side and titanium on the anolyte side; saidbipolar unit having a chamber for the collection of gases in the upperportion thereof, in Communication with the catholyte side of thebackplate, and a separate chamber for the collection of liquid in thelower portion thereof in communication with the catholyte side of thebackplatc; a plurality of hollow, wedge-shaped, inward and upwardlouvered, titanium anodes in said anolyte chamber, said titanium anodeshaving an electrically conductive surface only on the interior surfacesthereof; internally threaded titanium conductors between the base ofsaid titanium anode wedges and the titanium surface of said backplate;the bases of said hollow, inward and upward louvered, titanium anodewedges being held securely against said titanium conductors by athreaded, titanium screw; a plurality of hollow, wedge-shaped, ferrousmetal cathodes in said catholyte chamber; said hollow, wedge-shapedferrous metal cathodes being spaced from and electrically connected tothe ferrous metal surface of said backplate; the hollow, wedge-shaped,titanium anodes of one bipolar unit and the hollow, wedge-shapedcathodes of the next adjacent bipolar unit being interleaved between anduniformly spaced from each other and forming a single electrolytic celltherebetween; and an asbestos diaphragm on said hollow, wedge-shapedcathodes dividing said single electrolytic cell into an anolyte chamberand a catholyte chamber; which method comprises continuously feedingsodium chloride brine into each of said individual electrolytic cells;passing an electrical current through said electrolyzer from the cathodeof one cell through an electrode support means which extends through anopening in the backplate, to an anode mounting means, and from the anodemounting means to an anode of the next adjacent cell in theelectrolyzer; evolving and collecting chlorine within the hollow,wedge-shaped, anodes between the inward and upward louvered wallsthereof, thereby imparting an upward circulatory motion to anolyteliquor within the hollow, wedge-shaped anodes; recovering said chlorineat the top of said anolyte chamber; evolving hydrogen and caustic sodain said catholyte chamber; collecting the evolved hydrogen gas in thechamber in the upper portion of the bipolar unit; continuouslyrecovering chlorine from said chamber, and recovering catholyte liquorfrom the separate chamber in the lower portion of the bipolar unit.

* lt Il* i 1k

1. A METHOD OF OPERATING A BIPOLAR ELECTROLYZER HAVING A PLURALITY OFINDIVIDUAL BIPOLAR UNITS IN BACK-TO-BACK BIPOLAR CONFIGURATION, WITH APERIPHERAL WALL AROUND EACH INDIVIDUAL BIPOLAR UNIT: AN ANOLYTE CHAMBERAND A CATHOLYTE CHAMBER IN EACH INDIVIDUAL BIPOLAR UNIT, THE ANOLYTECHAMBER AND CATHOLYTE CHAMBER OF AN INDIVIDUAL BIPOLAR UNIT BEINGSEPARATED FROM EACH OTHER BY A BACKPLATE HAVING A SURFACE OF A FERROUSMETAL ON THE CATHOLYTE SIDE AND TITANIUM ON THE ANOLYTE SIDE: APLURALITY OF HOLLOW, WEDGE-SHAPED, INWARD AND UPWARD LOUVERD, VALVEMETAL ANODES IN SAID ANOLYTE CHAMBER, SAID VALVE METAL ANODES HAVING ANELECTRICALLY CONDUCTIVE SURFACE THEREON: VALVE METAL CONDUCTORS BETWEENTHE BASE OF SAID VALVE METAL ANODE WEDGES AND THE TITANIUM SURFACE OFSAID BACKPLATE: THE BASES OF SAID HOLLOW, WEDGE-SHAPED, INWARD ANDUPWARD LOUVERED, VALUE METAL ANODES BEING HELD SECURELY AGAINST SAIDVALVE METAL CONDUCTORS: A PLURALITY OF HOLLOW, WEDGE-SHAPED, METALCATHODES IN SAID CATHOLYTE CHAMBER: SAID HOLLOW, WEDGE-SHAPED METALCATHODES BEING SPACED FROM AND ELECTRICALLY CONNECTED TO THE FERROUSMETAL SURFACE OF SAID BACKPLATE: THE HOLLOW, WEDGE-SHAPED, VALVE METALANODES OF ONE BIPOLAR UNIT AND THE HOLLOW, WEDGE-SHAPED CATHODES OF THENEXT ADJACENT BIPOLAR UNIT BEING INTERLEAVED BETWEEN AND UNIFORMLYSPACED FROM EACH OTHER AND FORMING A SINGLE ELECTROLYTIC CELLTHEREBETWEEN: AND A DIAPHRAGM THEREBETWEEN DIVIDING SAID SINGLEELECTROLYTIC CELL INTO AN ANOLYTE CHAMBER AND A CATHOLYTE CHAMBER WHICHMETHOD COMPRISES FEEDING SODIUM CHLORIDE BRINE INTO EACH OF THEINDIVIDUAL ELECTROLYTIC CELLS: PASSING AN ELECTRICAL CURRENT THROUGHTHROUGH THE ELECTROL FROM THE CATHODES OF ONE CELL THROUGH THE BACKPLATETO THE ANODES OF THE NEXT ADJACENT CELL IN THE ELECTROLYZER: EVOLVINGCHLORINE IN THE ANOLYTE CHAMBER: COLLECTING THE EVOLVED CHLORINE WITHINTHE HOLLOW, WEDGE-SHAPED ANODES BETWEEN THE
 2. The method of operating abipolar electrolyzer of claim 1 wherein said hollow, wedge-shaped,inward and upward louvered, valve metal anodes have an electricallyconductive surface only on the interior surfaces thereof and whereinchlorine is evolved only within the hollow, wedge-shaped anodes.
 3. Themethod of operating a bipolar electrolyzer of claim 1 comprising passingthe electrical current from a cathode of one cell through an electrodesupport means which extends through an opening in the backplate, to ananode mounting means of the next adjacent cell of the electrolyzer, andfrom the anode mounting means to an anode mounted thereon.
 4. The methodof operating a bipolar electrolyzer of claim 1 comprising collecting theevolved hydrogen gas in a chamber in the upper portion of the bipolarunit and recovering catholyte liquor from a separate chamber in thelower portion of the bipolar unit.
 5. A method of operating a bipolarelectrolyzer having a plurality of individual bipolar units inback-to-back bipolar configuration, with a peripheral wall around eachindividual bipolar unit; an anolyte chamber and a catholyte chamber ineach individual bipolar unit, the anolyte chamber and catholyte chamberof an individual bipolar unit being separated from each other by abackplate having a surface of a ferrous metal on the catholyte side andtitanium on the anolyte side; a plurality of hollow, wedge-shaped,inward and upward louvered, titanium anodes, in said anolyte chamber,said titanium anodes having an electrically conductive surface only Onthe interior surfaces thereof; titanium conductors between the base ofsaid hollow, wedge-shaped, titanium anodes and the titanium surface ofsaid backplate; the bases of said hollow, wedge-shaped, inward andupward louvered, titanium anodes being held securely against saidtitanium conductors; a plurality of hollow, wedge-shaped, metal cathodesin said catholyte chamber; said hollow, wedge-shaped metal cathodesbeing spaced from and electrically connected to the ferrous metalsurface of said backplate; the hollow, wedge-shaped, titanium anodes ofone bipolar unit and the hollow, wedge-shaped cathodes of the nextadjacent bipolar unit being interleaved between and uniformly spacedfrom each other and forming a single electrolytic cell therebetween; anda diaphragm therebetween dividing said single electrolytic cell into ananolyte chamber and a catholyte chamber; which method comprises feedingsodium chloride brine into each of said individual electrolytic cells;passing an electrical current through said electrolyzer from thecathodes of one cell through the backplate to the anodes of the nextadjacent cell in the electrolyzer; evolving and collecting chlorinewithin the hollow, wedge-shaped anodes between the inward and upwardlouvered walls thereof, thereby imparting an upward circulatory motionto anolyte liquor within the anode wedges; recovering said chlorine atthe top of the anolyte chamber; evolving hydrogen and caustic soda inthe catholyte chamber; recovering said hydrogen at the top of thecatholyte chamber; and recovering catholyte liquor from the catholytechamber.
 6. The method of operating a bipolar electrolyzer of claim 5comprising passing the electrical current from a cathode of one cellthrough an electrode support means which extends through an opening inthe backplate, to an anode mounting means in the next adjacent cell, andfrom the anode mounting means to an anode mounted thereon.
 7. The methodof operating a bipolar electrolyzer of claim 5 comprising collecting theevolved hydrogen gas in a chamber in the upper portion of the bipolarunit and recovering catholyte liquor from a separate chamber in thelower portion of the bipolar unit.
 8. A method of operating a bipolarelectrolyzer having a plurality of individual bipolar units inback-to-back bipolar configuration, with a peripheral wall around eachindividual bipolar unit; an anolyte chamber and a catholyte chamber ineach individual bipolar unit, the anolyte chamber and catholyte chamberof an individual bipolar unit being separated from each other by abackplate having a surface of a ferrous metal on the catholyte side andtitanium on the anolyte side; a plurality of hollow, wedge-shaped,inward and upward louvered, valve metal anodes in said anolyte chamber,said valve metal anodes having an electrically conductive surface onlyon the interior surfaces thereof; valve metal conductors between thebase of said hollow, wedge-shaped, valve metal anodes, and the valvemetal surface of said backplate; the bases of said hollow, wedge-shaped,inward and upward louvered, valve metal anodes being held securelyagainst said valve metal conductors; a plurality of hollow,wedge-shaped, metal cathodes in said catholyte chamber; said hollow,wedge-shaped, metal cathodes being spaced from and electricallyconnected to the ferrous metal surface of said backplate, the hollow,wedge-shaped, valve metal anodes of one bipolar unit and the hollow,wedge-shaped cathodes of the next adjacent bipolar unit beinginterleaved between and unformly spaced from each other and forming asingle electrolytic cell therebetween; and a diaphragm therebetweendividing said single electrolytic cell into an anolyte chamber and acatholyte chamber; which method comprises feeding sodium chloride brineinto each of said individual electrolytic cells; passing an electricalcurrent through said electrolyzer from the cathode of one cell throughan electrode support means which extends through an opening in thebackplate, to an anode mOunting means, in the next adjacent cell, andfrom the anode mounting means to an anode mounted thereon; evolving andcollecting chlorine within the hollow, wedge-shaped, valve metal anodesbetween the inward and upward louvered walls thereof, thereby impartingan upward circulatory motion to the anolyte liquor within the hollow,wedge-shaped anodes; recovering said chlorine at the top of said anolytechamber; evolving hydrogen and caustic soda in said catholyte chamber;collecting the evolved hydrogen gas in a chamber in the upper portion ofthe bipolar unit and recovering the hydrogen gas therefrom; andrecovering catholyte liquor from a separate chamber in the lower portionof the bipolar unit.
 9. A method of operating a bipolar electrolyzerhaving a plurality of individual bipolar units in back-to-back bipolarconfiguration, with a peripheral wall around each individual bipolarunit; an anolyte chamber and a catholyte chamber in each individualbipolar unit, the anolyte chamber and catholyte chamber of an individualbipolar unit being separated from each other by a backplate having asurface of a ferrous metal on the catholyte side and titanium on theanolyte side; said bipolar unit having a chamber for the collection ofgases in the upper portion thereof, in communication with the catholyteside of the backplate, and a separate chamber for the collection ofliquid in the lower portion thereof in communication with the catholyteside of the backplate; a plurality of hollow, wedge-shaped, inward andupward louvered, titanium anodes in said anolyte chamber, said titaniumanodes having an electrically conductive surface only on the interiorsurfaces thereof; internally threaded titanium conductors between thebase of said titanium anode wedges and the titanium surface of saidbackplate; the bases of said hollow, inward and upward louvered,titanium anode wedges being held securely against said titaniumconductors by a threaded, titanium screw; a plurality of hollow,wedge-shaped, ferrous metal cathodes in said catholyte chamber; saidhollow, wedge-shaped ferrous metal cathodes being spaced from andelectrically connected to the ferrous metal surface of said backplate;the hollow, wedge-shaped, titanium anodes of one bipolar unit and thehollow, wedge-shaped cathodes of the next adjacent bipolar unit beinginterleaved between and uniformly spaced from each other and forming asingle electrolytic cell therebetween; and an asbestos diaphragm on saidhollow, wedge-shaped cathodes dividing said single electrolytic cellinto an anolyte chamber and a catholyte chamber; which method comprisescontinuously feeding sodium chloride brine into each of said individualelectrolytic cells; passing an electrical current through saidelectrolyzer from the cathode of one cell through an electrode supportmeans which extends through an opening in the backplate, to an anodemounting means, and from the anode mounting means to an anode of thenext adjacent cell in the electrolyzer; evolving and collecting chlorinewithin the hollow, wedge-shaped, anodes between the inward and upwardlouvered walls thereof, thereby imparting an upward circulatory motionto anolyte liquor within the hollow, wedge-shaped anodes; recoveringsaid chlorine at the top of said anolyte chamber; evolving hydrogen andcaustic soda in said catholyte chamber; collecting the evolved hydrogengas in the chamber in the upper portion of the bipolar unit;continuously recovering chlorine from said chamber, and recoveringcatholyte liquor from the separate chamber in the lower portion of thebipolar unit.